Mr Pennings said the $15 million price tag would be drawn from the council's existing general revenue.

"Before the election, like the parties, we'll be releasing our full costings, with regards to where we'll be saving money and spending money," he said.

"It's not a huge amount of money and we think it will make a big difference in the lives of people."

Mr Pennings said he was confident $15 million would be enough to implement the policy and that he would be able to get the support of Translink, which remained responsible for fares.

"The best way for council to do this, if Translink refuses to do it, is to (renegotiate the terms of) Brisbane City Council's contract with Translink, with the next one due later this year," he said.

"With the next contract due this year, the council can give that ($15 million) over for that purpose.

"Translink would be crazy to say 'no' because they'd be stopping what council was voted in to do."

Mr Pennings said the Greens had also committed to fast-track the council's bus stop accessibility program by three years, with a completion date later this year.

"We understand that the journey starts before you get on the bus," he said.

"Bus stops need shade, shelters and appropriate seating to make bus travel suitable for all passengers, especially seniors and people with mobility impairments."

Mr Pennings said the policies were the first of 10 major weekly announcements that would be made in the lead-up to the March 19 poll.

But if previous election results were anything to go by, the Greens faced an uphill battle to implement their policies.

The party's 2012 lord mayoral candidate, former Democrats senator Andrew Bartlett, attracted just 10.7 per cent of the primary vote at that election up against Lord Mayor Graham Quirk and Labor candidate Ray Smith.

Candidate Jo-Anne Bragg almost reached double figures in 2008, against incumbent Campbell Newman and Labor candidate Greg Rowell, when she attracted 9.8 per cent of the primary vote.

* CORRECTION: A previous version of this article incorrectly stated Andrew Bartlett 8.1 per cent of the primary vote in 2012.